Social integration, that is, participation in multiple social roles, is associated with reduced morbidity and mortality risk. Midlife appears to be a critical period for observing these effects, as social networks are most robust during this stage of life, and health declines after middle age. Evidence suggests that social integration may be important in regulating emotion, in promoting health behavior, and in modulating biological processes that may be related to disease. Little is understood, however, about how daily social interactions may contribute to these effects. In this study, we will follow a group of 400 community adults over a one-week period, sampling daily social interactions concurrently with affective, behavioral, and biological markers of health risk. We will examine whether socially integrated people show more adaptive patterns of emotion, health behavior (diet, physical activity, smoking, and alcohol use), and physiology (ambulatory blood pressure, cortisol, metabolic and inflammatory responses). We will also examine how features of daily social interaction, including the diversity of social role interactions during daily life, and the frequeny of contact with others who exhibit negative health behaviors, may contribute to these effects. We will examine the extent to which socially integrated people are relatively protected from the effects of stress and social pressures when it comes to these measures, and we will examine the extent to which some of the effects we observe may be accounted for, in part, by associated features of the person (cognitive style or personality traits) or the nature of their daily activites.